Printer media with bar code identification system

ABSTRACT

A bi-directionally scannable bar code pattern having a parallel array of alternating lines and spaces, each having selected widths. Each line has a common series of segments and segment spaces of selected lengths. The length of each segment may be the same as the width of a corresponding line, and the length of each segment space may be the same as the width of a corresponding space between lines. The pattern may be printed on a sheet of printer media, or on a strip attached to such a sheet.

This application is a Division of Ser. No. 09/034,787, filed Mar. 4,1998 , U.S. Pat. No. 5,984,193.

FIELD OF THE INVENTION

This invention relates to printer media and computer printers, and moreparticularly to printed indicia for automatic identification of media bya printer.

BACKGROUND AND SUMMARY OF THE INVENTION

Computer printers such as ink jet printers often use different printingtechniques for different types of printer media, such as conventionalpaper, specialized ink jet paper, coated paper, and transparencies.Depending of the media characteristics, different printing algorithmsare used to prevent undesirable image characteristics such as color inkbleed, which varies with media type.

In addition, a given printer may be used for printing on different sizesof media. In such cases, it is helpful for the image printed to be sizedto fit the media. This avoids images bleeding off the sheet edge,requiring two sheets, or failing to fill the full sheet area if desired.Also, dual sided or duplex printing requires careful manual reloading ofthe media supply during the printing process, with errors frequentlyoccurring due to misorienting the media stack.

While paper size, type, and orientation may be properly established andmanually entered into the printer memory or connected computer by analert user, it is desirable to automate such tasks to simplify operationand to avoid likely errors. Existing media has been provided with barcoded identifying data for scanning by a printer. Such bar codes aretypically provided at the corner margins of sheets on both sides, andare printed in a normally invisible fluorescent ink. The bar code inkfluoresces at an infrared wavelength in response to illumination by ared emitter in the printer, and is read by an optical scanner in theprinter.

A typical printer drives paper along a feed axis, and has a print headcarriage reciprocating over the paper along a perpendicular scan axis.In some printers, the bar code sensor is stationary, and mounted to theprinter chassis at the edge of the paper path. Such fixed sensors may bereadily shielded from exterior light, and may read a bar code as thepaper is initially fed along the feed axis before the carriage begins toreciprocate. The lines of the bar code on the paper must be orientedperpendicular to the feed axis for use with a fixed sensor. In otherprinters, the sensor is mounted on the carriage, so that it may alsoperform other sensing functions such as media edge detection and inkcolor registration procedures. For carriage mounted sensors, the barcode lines on the media sheet must be oriented perpendicular to the scanaxis. Bar coded media for one type of printer sensor is not necessarilycompatible with the other type of sensor, requiring inventory of twomedia code types, and possible user confusion.

Transparencies present an additional challenge, as they are unsuitablefor printing invisible bar codes. A paper strip may be attached to amargin of the film for printing indicia, but such a sheet will belimited for use only with a given type of printer sensor.

The present invention overcomes the limitations of the prior art byproviding a bi-directionally scannable bar code pattern having aparallel array of alternating lines and spaces, each having selectedwidths. Each line has a common series of segments and segment spaces ofselected lengths. The length of each segment may be the same as thewidth of a corresponding line, and the length of each segment space maybe the same as the width of a corresponding space between lines. Thepattern may be printed on a sheet of sprinter media, or on a stripattached to such a sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified perspective view of a media sheet according to apreferred embodiment of the invention as received in a printer.

FIG. 2 is a plan view of a strip printed with a set of coded graphicalelement according to the embodiment of FIG. 1.

FIG. 3 is a plan view of a coded graphical element according to theembodiment of FIG. 1.

FIG. 4 is a perspective view of a transparency media sheet with a codedstrip according to the embodiment of FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 shows a computer printer 10 into which a sheet of printer media12 has been loaded. The printer has a media drive mechanism 14 thatfeeds the sheet along a paper path, with motion of the sheet defining afeed axis 16. A print head carriage 20 reciprocates along a scan axis 22on a guide rod 24, and carries a print cartridge 26 that expels inkdroplets onto the media surface. The scan axis is perpendicular to thefeed axis. The printer includes a carriage-mounted optical sensor 30 aor a fixed optical sensor 30 b mounted to the printer frame. Eitheroptical sensor is positioned to read conventional bar codes.

A carriage mounted sensor 30 a has fine resolution along the scan axisto read bar code symbols with lines oriented perpendicular to the scanaxis. The motion of the carriage moves the sensor across the bar codelines to read the code. A fixed sensor 30 b is positioned near the edgeof the media path, and overhangs the media to read a bar code along theside edge of the media. With fine resolution along the feed axis, thesensor reads bar code symbols having lines oriented perpendicular to thefeed axis as the media sheet moves relative to the sensor.

Regardless of sensor position, the sensor may be of any type suitablefor reading a bar code, such as one that illuminates or detects a smallspot, or one that illuminates or detects a narrow line parallel to thelines of a conventional bar code. In the preferred embodiment, thesensor provides illumination and sensing to detect patterns printed onthe media in “invisible ink” that fluoresces in the infrared in responseto illumination with a red emitter. Alternative invisible inks may beused, as may visible inks or other detectable characteristics.

While the printer sensor may be of different alternative configurations,the media sheet 12 is encoded with a pattern 32 that may be detected byeither type of sensor, and regardless of orientation of the sheet. Thepattern is an elongated stripe that extends along the length of theleading edge of the sheet. In alternative embodiments, the pattern maybe printed on some or all sheet edges, on one or both faces of thesheet, or at selected marginal positions on the sheet, such as at thecorners. The pattern may be formed of a multitude of identical elementsso that the same information is read by a sensor reading any portion ofthe sheet. Alternatively, the pattern may have different patternsprinted to different portions of the sheet, to distinguish between facesof the sheet, or between leading and trailing edges, to ensure propersemi-manual duplex printing.

FIG. 2 shows details of the pattern 32 as printed at the edge of a mediasheet or strip 34. For paper media, the pattern is printed directly onthe media; for transparent media, the pattern is printed on a paperstrip attached to an edge of the transparency. The pattern includes arepeating linear array of closely spaced pattern elements or tiles 36alternating with separator elements 37. The pattern elements abut eachother and are registered in a straight line parallel to the edge of thesheet or strip. The tiles 36 have bi-directional bar codes, as will bediscussed below, while the separator elements 37 have bar code linesonly in complete rows parallel to the length of the pattern 32, in themanner of a conventional bar code.

Accordingly, a carriage mounted scanner will be able to identify thebeginning of the the code pattern by detecting the unprinted columnsfollowing a section of identical columns. In the illustrated instance,the tile code begins with an initial “1,0” identifier, although otherpatterns may be used. A fixed sensor will read the separator tiles 37just as readily as the bi-directionally coded tiles 36, so thatregistration of the pattern 32 with the sensor is not required.

FIG. 3 shows a single tile 36, which contains an encoded value that isscannable in either orthogonal direction. In the illustrated embodiment,the tile is a 10 by 10 matrix of square pixels. Although illustratedwith spaces between the pixels for clarity, the pixels preferably abuteach other. Each pixel may either be unprinted for a “0” value, orprinted for a “1” value. Each row and column has either all unprintedpixels, or a common sequence of selectably printed and unprinted pixelscorresponding to the encoded value, in this case “1,0,1,0,1,1,0,1,1,1”.As a consequence of this requirement, a row or column remains entirelyunprinted if its ordinal position corresponds to a “0” in the encodedsequence. The encoding algorithm may also be expressed as a requirementthat a pixel be printed only if its column and row ordinal positionsboth correspond to a “1” value on the encoded sequence. Because the rowsand columns are subject to the same encoding rules, the pattern issymmetrical about a diagonal axis 40 that connects pixel (1,1) to pixel(10,10).

Each printed column is said to be a printed line, and is read as such bya conventional slit sensor, even though the line is broken into a seriesof line segments, some of which may be single pixel dots. The unprintedcolumns and rows are considered as unprinted lines. The pattern elementor tile is shown as a matrix with pixels on a uniform pitch, providingline or line segment widths at an integral multiple of the pitch.Alternatively, the widths and spaces may be varied over a range ofdetectable values to encode more information, in the manner of aconventional bar code. In any case, the pattern element is theconceptual equivalent to printing two identical bar code patternsoverlaying each other, with a 90 degree offset, and removing allprinting except where printed by both patterns. Another conceptualequivalent is starting with a fully printed tile, and removing stripeswhere spaces are desired, for each direction. In an alternativeembodiment, the tile may be generated with each pixel being printed ifeither its row or column or both have a value of “1”. Instead of dotsand dashes on an unprinted field, the pattern may be a solid printedblock perforated by unprinted dots and dashes. This approach is lessdesirable because an average tile will be about 75% printed, instead ofthe 25% printed tiles of the illustrated embodiment.

In alternative embodiments, each tile may be printed with a differentcode in different axes. One embodiment of this might include the samepaper size code in each direction, but a different orientation indicatorfor the printer controller to determine how the media has beeninstalled. The tiles need not be square, and may be rectangular, withline and space widths proportional to, but not necessarily equal to eachother.

In FIG. 4, the media 12 is a transparency film with the patterned strip34 adhered at one edge. The strip is continuously printed with thepattern 32, and may be drawn from a continuously printed strip roll 42having a length adequate to provide strips for a multitude of sheets.The disclosed pattern is well suited to this method of preparing mediabecause registration of the pattern is not required. Elongated tapes arelikely to experience linear dimensional variations that accumulate overa lengthy roll, making precise cutting and registration impractical. Aprinter that scans the strip across the length of the strip (such as ina fixed sensor printer) will be entirely insensitive to the position ofthe strip; a carriage mounted scanner will proceed until it finds thefirst or any complete pattern element. A partial pattern elementresulting from imprecise cutting or misalignment will have no harmfuleffect.

The pattern is intended for any printer with a slit type sensor thatdetects a region preferably less than or equal to one pixel wide, atleast two pixels long if the pattern algorithm is limited to no morethan one consecutive “0” value, and longer if consecutive zeros aretolerated. However, the pattern may also be scanned by a round or squarespot sufficiently larger than the widest possible swath of unprinted “0”values to ensure that a spot centered on the swath will detect theadjacent printed lines to determine their printed and unprinted linesegments.

While the above is discussed in terms of preferred and alternativeembodiments, the invention is not intended to be so limited. Forinstance, the pattern is discussed in terms of printed and unprintedportions, these terms are used for illustration only. Any selectablecharacteristic detectable by a sensor may be used. Printed ink havingdifferent reflectance or emission characteristics is the preferredembodiment (with the black portions of the illustrations representingmore emissive fluorescent ink). Alternatives may include media texture,contour, electrical charge, magnetic characteristics, or any otherdetectable value. In any embodiment, the characteristic representing a“1” value and that representing a “0” value may be switched, so thoseareas described as “printed” may in fact be bare media, while thatdescribed as “unprinted” has a substance applied, or distinctcharacteristic relative to the media surface.

What is claimed is:
 1. A printer media element comprising: a rectangularsheet having opposed major faces and four peripheral edges; the sheethaving an elongated edge surface portion extending parallel to andproximate to a selected peripheral edge of the sheet; the edge surfaceportion being imprinted with a bi-directionally linearly scannable barcode pattern having a plurality of bar code sub-elements, each subelement comprising: a parallel array of alternating elongated firstportions and second portions; each of the first portions having a firstoptical characteristic, and each of the second portions having adistinct second optical characteristic; each of the first portions andeach of the second portions having a respective selected width selectedfrom a range of different widths; each of the first portions comprisingan elongated bar having a common series of alternating first segmentsand second segments; each of the first segments having the first opticalcharacteristic, and each of the second segments having the secondoptical characteristic; each of the first segments and each of thesecond segments having a selected length; the length of each firstsegment in the series being equal to the width of a corresponding firstportion at a corresponding place in the array, and the length of eachsecond segment in the series being equal to the width of a correspondingsecond portion at a corresponding place in the array.
 2. The pattern ofclaim 1 wherein the pattern is symmetrical about a diagonal axis.
 3. Thepattern of claim 1 wherein the optical characteristic is fluorescence.4. The pattern of claim 3 including multiple instances of the patternprinted along an edge of the sheet.
 5. The pattern of claim 3 whereinthe sheet is an elongated strip, and wherein multiple instances of thepattern are printed along the strip.
 6. The printer media element ofclaim 1 wherein a sequence of widths of the printed portions and theunprinted portions corresponds to a sequence oflengths of the printedsegments and the unprinted segments.
 7. The printer media element ofclaim 1 wherein the sheet is a transparency having a paper stripcomprising the edge surface portion.
 8. The printer media element ofclaim 7 wherein the graphic elements are printed along the entirelengths of the strip.
 9. The printer media element of claim 8 whereinthe coded pattern bleeds off the ends of the strips.
 10. A method ofmanufacturing a sheet of printer media comprising: providing a sheet;generating an encoded pattern along an edge portion of the sheet; theencoded pattern including a graphic element having an array ofalternating linear unprinted portions and printed portions, each of theprinted portions and unprinted portions being of a selected widthselected from a range of widths; the printed portions and unprintedportions of each graphic element being oriented in a parallel array,each printed portion and each unprinted portion oriented perpendicularto the length of the elongated edge surface portion of the sheet; eachof the printed portions comprising an elongated bar comprising a seriesof alternating printed segments and unprinted segments; and each of theprinted segments and unprinted segments being of a selected lengthselected from a range of lengths.
 11. The method of claim 10 whereingenerating the graphically encoded pattern includes printing acontinuous series of the graphic elements on an elongated strip having alength at least several times greater than the length of the edgeportion of the sheet, and applying a segment of the strip to the sheet.12. The method of claim 11 wherein the sheet is a transparency film. 13.The method of claim 10 wherein each of the graphic elements issymmetrical about an axis of symmetry diagonal to the printed portionsand to the edge surface portion.
 14. The method of claim 10 wherein asequence of widths of the printed portions and the unprinted portionscorresponds to a sequence of lengths of the printed segments and theunprinted segments.
 15. A printer media element comprising: arectangular sheet having opposed major faces and four peripheral edges;the sheet having an elongated edge surface portion extending parallel toand proximate to a selected peripheral edge of the sheet; the edgesurface portion being imprinted with a bi-directionally linearlyscannable bar code pattern having a plurality of bar code sub-elements,each sub element comprising: a parallel array of alternating elongatedfirst portions and second portions; each of the first portions having afirst optical characteristic, and each of the second portions having adistinct second optical characteristic; each of the first portions andeach of the second portions having a respective selected width selectedfrom a range of different widths; each of the first portions comprisingan elongated bar having a common series of alternating first segmentsand second segments; each of the first segments having the first opticalcharacteristic, and each of the second segments having the secondoptical characteristic; each of the first segments and each of thesecond segments having a selected length; the length of each firstsegment in the series being equal to the width of a corresponding firstportion at a corresponding place in the arrray; and the length of eachsecond segment in the series being equal to the width of a correspondingsecond portion at a corresponding place in the array.
 16. The pattern ofclaim 15 wherein the pattern is symmetrical about a diagonal axis. 17.The pattern of claim 15 wherein the optical characteristic isfluorescence.
 18. The pattern of claim 17 including multiple instancesof the pattern printed along an edge of the sheet.
 19. The pattern ofclaim 17 wherein the sheet is an elongated strip, and wherein multipleinstances of the pattern are printed along the strip.